Vegetation Conditions

The Owens Valley Monitor 2002-2003

Vegetation Conditions - continued

    In contrast with the Control group, perennial cover was statistically significantly less than baseline for both wellfield groups (DRP and DRPfree) when averaged for all parcels (Figure 3). Average perennial cover has been statistically significantly less than baseline since 1999 for the DRP parcels and has been at or below baseline during all twelve years. For the first time since the DRPfree group was created (1996), perennial cover averaged statistically significantly below baseline (Figure 3).
     It remains to be seen if the suppressed cover will continue or whether the response for the DRPfree group is intermediate between that of the Control and DRP group. Water levels in some DRPfree parcels remained more or less constant between 2001 and 2002, but for others, water levels may have been lowered due to recent pumping. Splitting the DRPfree group into two or more groups that more appropriately depict management conditions may be warranted, but depends on acquisition of sound water table estimates.
     At the scale of the individual parcel, adequate depth to water table estimates exist for about half of the parcels inventoried in 2002. Examples of vegetation and water table conditions through time are provided in Figure 4.

Table 5. Change in perennial cover relative to baseline for Control, DRP, DRPfree and more study parcels, broken down by wellfield. For example, if a parcel’s baseline cover was 30% and its 2002 cover was 15%, the change relative to baseline would be -50.00. Bold entries show when a paired (dependent) t-test revealed a statistically significant difference at p <= 0.05 between baseline perennial cover and 2002. The standard error of the change value is presented as well as the number of parcels in each group. Values shown with shading are graphed in Figure 3.

	Avg. % change relative to baseline	Standard error	No. of parcels	Avg. % change relative to baseline	Standard error	No. of parcels
All Control parcels	-7.42	(6.72)	30
Category	DRP			DRPfree
Wellfield
Laws	-59.43	(11.29)	8	-14.61	(14.02)	7
Bishop	-30.54	(5.43)	2	-34.99	(5.38)	4
Big Pine	-63.44	(6.60)	3	-16.90	(15.59)	6
Taboose Aberdeen	-49.84	(8.19)	6	-9.36	(6.85)	7
Thibaut Sawmill	-47.34	(9.25)	4	-21.00	(3.08)	4
Independence Oak	2.59	(39.04)	2	-31.20	(1.13)	2
Symmes Shepherd	-47.54	(5.55)	5	-21.36		1
Bairs Georges	-82.10		1			1
Lone Pine				-63.54
ALL	-49.35	(4.95)	31	-20.02	(4.72)	32

	More study
Independence Oak	-61.20	(5.62)	3

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